This invention relates to a cam grinding machine used chiefly for working on a workpiece having plural cam blocks for producing a valve driving cam shaft of an internal combustion engine or the like.
Grinding machines have been known which include a swingable table provided thereon with a turnable work shaft for holding a workpiece. The table is arranged to be controlled in its swing movement by a touch roller means and a master cam means which are disposed to face one another between the table and a machine frame. The machine frame is provided opposed to the table so that the workpiece may be ground by a turning grinding wheel which is disposed on the forward side in the forward and rearward swing direction of the table. It has been usual with this type of machine that the master cam means is provided on the table so as to be turnable synchronously with the turning of the work shaft, and the touch roller means is provided on the machine frame. It has been usually practiced with this arrangement that, when the workpiece having plural cam blocks different in phase from each other is to be ground, a master cam means composed of plural master cam members corresponding in phase to the respective cam blocks is used. The respective cam blocks are ground one by one by bringing the respective master cam members of the master cam means one by one into contact with the touch roller means. This however, is inconvenient in the following points:
(i) The same number of the master cam members as that of the cam blocks of the workpiece is required, so that it takes much trouble and time to manufacture the master cam members.
(ii) As a result of the fact that the plural master cam members are mounted on the swingable table, the swing inertia weight of the table is increased. If the grinding is carried out at a high speed, there occurs a jumping phenomenon because of a delay in swing movement of the table.
In order to decrease the number of the master cam members mounted on the swingable table, another grinding machine is known wherein the master cam shaft is connected to the work shaft through a phase adjacent mechanism such as a rotary actuator or the like so that grinding of plural cam blocks of the workpiece different in phase may be carried out using a single common master cam member by means of a phase adjustment of the cam shaft. (See Japanese Patent Publication Sho. No. 56-8740). In this type of machine, the foregoing first inconvenience can be removed, but the foregoing second inconvenience cannot be removed, because the weight of the phase adjustment mechanism is added to the table swing inertia weight. In addition, there is brought about a third inconvenience wherein when the workpiece is changed to a different kind of one, both the master cam means and the work shaft connected thereto through the phase adjustment mechanism are required to be replaced. Consequently, it takes much trouble and time to replace them. This is not suitable especially for production of worked products of various kinds with each kind being produced on a small scale.